The present invention relates to a measuring device according to the precharacterizing clause of Patent claim 1.
In many situations, for measuring material thicknesses for example, use is made of a type of measuring device in which a measuring head is supported movably in a measuring housing and the measuring head is held at a certain distance from a measurement object by means of air which is blown out between the measuring head and the measurement object and there forms an air cushion. By means of such an air cushion, the gap between the measuring head and the measurement object can be kept small and constant, which is advantageous for measuring accuracy.
It is also important for the measuring accuracy, however, that the measuring head is easily movable in the measuring housing, which is usually mounted in a fixed manner. Supporting the measuring head by means of air makes it possible for the measuring head to move easily in the measuring housing, but, in order to achieve sufficiently good mobility and thus the possibility of good measuring accuracy, it is also necessary for electric wires between the measuring head and the measuring housing to be made very flexible so as to afford low movement resistance of the measuring head. This in turn results in these wires being very delicate and in relative rotation between the measuring head and the measuring housing having to be limited so as not to damage the wires.
Against this background, it has been proposed that the measuring housing be provided with axial grooves and the measuring head be provided with heels fitting these grooves in order in this way to limit relative rotation between the measuring head and the measuring housing. In this connection, however, problems of friction between the grooves and the guide heels arise in certain working positions of the measuring device, in spite of the measuring head being supported by air. Having a measuring head and a measuring housing of noncircular cross section has also been tried in order in this way to limit relative movement between them, but problems of friction have also arisen in this case and led to impaired measuring accuracy.
An object of the invention is to produce an improved measuring device which makes possible increased reliability and increased measuring accuracy. Another object is to achieve this by simple means.
The object of the invention is achieved by means of a measuring device having the features indicated in Patent claim 1.
By providing the measuring head with axial guide means which run in axial channels in the measuring housing, it is possible, by means of air, to hold the guide means in an easy-running manner in the channels in changing working positions of the measuring device. In this way, good mobility of the measuring head in different situations is ensured. The embodiment selected also makes manufacture and assembly of the measuring device easier.
Further features and advantages of the invention emerge from the description and patent claims below.
The invention will be described in greater detail below by means of an exemplary embodiment shown in the appended drawing.